An air-conditioning apparatus, such as a multi-air-conditioning apparatus for an office building, has been developed which conditions air by, for example, allowing a refrigerant circulating between an outdoor unit and a relay unit to exchange heat with a heat medium, such as water, circulating between the relay unit and an indoor unit. This apparatus reduces conveyance power for the heat medium and thus saves energy. (refer to Patent Literature 1, for example).
Another air-conditioning apparatus has been developed which takes measures against refrigerant leakage in the use of hydrocarbon as a refrigerant. In this air-conditioning apparatus, a solenoid valve blocks a refrigerant passage upon refrigerant leakage (refer to Patent Literature 2, for example).
Furthermore, another air-conditioning apparatus has been developed which avoids an explosion upon refrigerant leakage in the use of a flammable refrigerant. In this air-conditioning apparatus, when a refrigerant leakage sensor, disposed in an outdoor unit housing, detects the leakage of the refrigerant, a damper for discharging refrigerant is activated. An air-sending device is then activated so as to send air into the housing (refer to Patent Literature 3, for example).